docs: def sign_item(encrypted_item, signing_key, crypto_config):
      # type: (dynamodb_types.ITEM, DelegatedKey, CryptoConfig) -> dynamodb_types.BINARY_ATTRIBUTE
      """Generate the signature DynamoDB atttribute.
  
      :param dict encrypted_item: Encrypted DynamoDB item
      :param DelegatedKey signing_key: DelegatedKey to use to calculate the signature
      :param CryptoConfig crypto_config: Cryptographic configuration
      :returns: Item signature DynamoDB attribute value
      :rtype: dict
      """
      signature = signing_key.sign(
          algorithm=signing_key.algorithm,
          data=_string_to_sign(
              item=encrypted_item,
              table_name=crypto_config.encryption_context.table_name,
              attribute_actions=crypto_config.attribute_actions,
          ),
      )
      return {Tag.BINARY.dynamodb_tag: signature}